Nonlocal correlations in a proximity-coupled normal metal

TL;DR

This paper demonstrates long-range nonlocal correlations in superconductor/normal-metal heterostructures mediated by proximity effects, revealing phenomena beyond traditional superconducting correlations and suggesting new quantum effects at low temperatures.

Contribution

It presents the first evidence of nonlocal correlations in normal metals mediated by proximity coupling, extending the understanding of quantum correlations in hybrid structures.

Findings

Nonlocal voltage observed in normal metals separated by superconductor.

Nonlocal correlations extend over longer distances than in superconducting cases.

Reduction in nonlocal voltage at very low temperatures indicates new quantum effects.

Abstract

We report evidence of large, nonlocal correlations between two spatially separated normal metals in superconductor/normal-metal (SN) heterostructures, which manifest themselves a nonlocal voltage generated in response to a driving current. Unlike prior experiments in SN heterostructures, the nonlocal correlations are mediated not by a superconductor, but by a proximity-coupled normal metal. The nonlocal correlations extend over relatively long length scales in comparison to the superconduncting case. At very low temperatures, we find a reduction in the nonlocal voltage for small applied currents that cannot be explained by the quasiclassical theory of superconductivity. We believe is a signature of new long-range quantum correlations in the system.